1. Field of the Invention
This invention relates to a concentric magnetic configuration for loudspeakers which is designed to produce multiple air gap magnetic fields and which is capable of driving the full-range of high, medium, and low frequency voice coils from a single source magnet.
2. Background
In general, a speaker produces sound by converting an electrical signal into sound waves and radiating the sound waves into free space. When an electric current is caused to flow through a voice coil disposed in a strong magnetic field, a force is generated to cause a vibrating plate to radiate the sound wave.
With conventional loudspeaker magnetic circuit designs known in the art, only one air gap magnetic field is produced from one magnet. As is well known, it is physically difficult to produce a full range of high quality sound frequency from a single voice coil. Therefore, it is necessary to provide separate multiple magnets to reproduce the high, medium and low frequency sounds. Essentially, it is necessary to provide two or three separate speaker systems for each frequency sound, and then physically place these separate speaker systems in one acoustic loudspeaker box (generally referred as a xe2x80x9cseparate speaker systemxe2x80x9d hereinafter). Thus, a loudspeaker known in the art is designed to include a tweeter for the high frequency sound, a squawker for the middle frequency sound, and a woofer for the low frequency sound.
However, the size of a speaker cabinet to accommodate all of these separate speaker systems must, by necessity, be quite large and heavy, thus increasing the cost of the loudspeaker. Further, the quality of sound produced form the separate speaker system is often compromised, and not ideal since the high, medium, and low frequency sounds originate from different physical locations or separately located multiple magnets. Still further, synchronization of these different frequency sounds is necessary, further increasing the cost and complicating the. manufacturing process.
Attempts have been thus made to design a loudspeaker capable of producing different frequency sounds without having to utilize a separate speaker system as disclosed in, for example, U.S. Pat. No. 4,164,631, European Patent No. 0 341 926 A1 as well as China Patent Nos. ZL93242815.0, ZL92232080.2, ZL96213090.7, and ZL90216262.4. The systems disclosed in these patents still, however, have problems of being large in size, complex in their configurations, and high in cost. Further, prior to the present invention disclosed and claimed herein, there was no practically useful magnetic configuration which could produce the full range of high, medium and low frequency sounds from a single source magnet.
The present invention relates to a novel design of a single source magnetic configuration for loudspeakers which can produce a full range of sound frequency. In one embodiment, the magnetic configuration is concentric in shape and is adapted to be installed inside of loudspeakers. A cylindrical permanent magnet is provided as a source magnet and multiple air gap magnetic fields are produced to drive the full-range high, medium, and low frequency voice coils from the single magnet. The multiple air gap magnetic fields are produced by placing a high frequency pole plate and one or more middle yoke iron plates directly on the cylindrical permanent magnet. With flux controlling slots in various sizes configured beneath the high frequency pole plate and middle yoke iron plates, the high, medium, and low frequency air gap magnetic fields are achieved with the magnetic configuration of a single magnet.
The unique design of the magnetic configuration is significantly advantageous over traditional ways of creating magnetic fields based on the one magnet/one air gap formula. The magnetic configuration of the present invention design may be used for various speaker systems to provide ideal sound quality in a convenient and inexpensive manner.